The present invention relates to a resin molding method and a resin molding apparatus for molding resin by feeding molten resin into a cavity through molten-resin passages such as a sprue portion and a runner portion from a resin supply portion.
In a conventional molding process, an injection nozzle (i.e., molten-resin supply portion) is provided at an end of a cylinder and the molten resin held within the cylinder is supplied from the injection nozzle into a cavity through molten-resin passages such as a sprue portion, a gate portion and a runner portion. Then, an interior of the cavity is cooled down to a predetermined temperature so that the resin held within the cavity is solidified or cured to produce a molded article. Subsequently, molding dies are separated to open the cavity and the molded article is removed away from the cavity.
In this case, in the conventional molding process, an unnecessary additional material which is molded in the molten-resin paths and which is referred to as a runner (i.e., a sprue runner) is unavoidable at the time when the molded article is removed.
Conventionally, since the "runner" is wasted, in order to save the material, the runner is pulverized and reused.
However, a runner removal work and a sorting work to sort the runner and the molded article are so troublesome and a recycle system is very complicated.
For this reason, a so-called hot runner system has been developed in which the molten-resin paths are always heated in molding, and the runner is forcibly caused not to be solidified so that the runner is not discharged.
However, in the runnerless system such as the hot runner system, since the heating means has to be provided around the cavity which is intrinsically or inherently cooled, a heat-insulating structure has to be interposed between the heating means and the cavity, as a result of which a total cost is unduly increased. This system is not practical.
Accordingly, in general, the former system has been widely used in which the runner is removed and reused for molding.